Lithium depletion and angular momentum transport in F-type and G-type stars in Galactic open clusters

TL;DR

This study models angular momentum and lithium depletion in F- and G-type stars within open clusters, successfully explaining rotation and Li7 surface abundance patterns, but highlighting the need for improved turbulence modeling.

Contribution

It extends a previous stellar transport model to a broader range of stellar types and metallicities, accurately reproducing observed rotation and lithium depletion behaviors.

Findings

Reproduces the evolution of surface rotation rates across various stellar parameters.

Predicts the anti-correlation between rotation speed and Li7 depletion.

Highlights the dependence of Li7 dip reproduction on shear turbulence prescriptions.

Abstract

Open clusters provide clues to understand the evolution of Li7 at the surface of low-mass stars and its possible correlation with stellar rotation, which is a challenge for both stellar hydrodynamics and Galactic chemical evolution. We aim to quantify the efficiency of the transport processes for both angular momentum and chemicals that are required to explain simultaneously the observed behaviour of surface Li7 and rotation as well as the internal rotation profiles inferred from helio- and asteroseismology in F- and G-type main sequence stars. We apply the model for the transport of angular momentum and chemicals that we tailored in a previous work for solar-type stars to an extended range of initial masses and metallicities corresponding to F- an G-type stars in a sample of 20 Galactic open clusters. We evaluate its ability to explain the Li7, Be9, and rotation periods observations. Over the entire range of masses, metallicities, and ages explored, we reproduce the evolution of the surface rotation rates and predict, for the first time, the observed anti-correlation between the surface rotation rate and Li7 depletion as a consequence of the penetrative convection prescription. However, the ability of the model to reproduce the so-called Li7 dip centred around 6600K strongly depends on the adopted prescriptions for shear turbulence. It also requires a stellar mass dependence for the viscosity adopted for the transport of angular momentum, similar to the behaviour predicted for the generation and luminosity of internal gravity waves generated by stellar convective envelopes. We provide an efficient way to model G-type stars of different ages and metallicities successfully. However, the Li7 and Be9 dip constraints call for further hydrodynamical studies to better model turbulence in stars.